1. Field of the Invention
The invention relates to an implantable transducer for hearing aids which transducer operates using the electromagnetic transducer principle, and to a process for tuning the frequency response of the transducer.
2. Description of Related Art
Transducers of this type are known fundamentally, for example, from HNO, 1997-45:792-800, H. Leysieffer et al. “An implantable piezoelectric hearing aid transducer for those suffering from labyrinthine deafness.” This article is concerned especially with piezoelectric transducers, it is, however, generally pointed out that actuator hearing aid transducers also can be implemented using the electromagnetic transducer process. That is, in such an electromagnetic transducer a permanent magnet moves in the field of a stationary coil, whose field changes in time, which has the advantage of a miniaturization capacity of the movable permanent magnet.
One embodiment of an electromagnetic transducer which is designed for an at least partially implantable hearing aid for direct mechanical excitation of the middle ear or inner ear is described in U.S. Pat. No. 6,162,169. This patent discloses a permanent magnet which is suspended on the inside of a membrane and extends into a housing-mounted electromagnetic component, particularly a ring coil. The membrane, which closes the open face side of a hermetically sealed pot-shaped transducer housing, can vibrate. A coupling element for transmission of vibrations to the middle ear and/or the inner ear is mounted on the outside of the membrane.